8 



else than some form of molecular excitation, be it electronic, vi- 

 brational, or rotational. So what we biologists can safely do with- 

 out getting into an argument with statistical mechanics is to use 

 different symbols for bond energies which are linked to molecules 

 and have no outward action, and excitation energies which are 

 mobile and may interact with their surroundings. The former I 

 will denote by (£), meaning by E energy and symbolizing by the 

 parentheses that this energy is enclosed within a molecule. Excita- 

 tional energy I will denote £*. So I can formulate our problem 

 by asking whether, in muscle tlie (£) of the --^P in ATP is not 

 exchanged for £* when it has to go into biological action and pro- 

 duce contraction.^ Group transfer reactions of intermediary metab- 

 olism could be symbolized by writing: 



(En) ^ (£3) ^ (£2) ^ (El) where (£„) stands for the en- 

 ergy of reserve food as fat and carbohydrate while (Ex) stands for 

 the energy of the substance which is directly fed into the muscle 

 machine, in our case ATP. In this row of reactions the potential 

 energy is transferred from bond to bond, from substance to sub- 

 stance. Bond creating bond, these reactions can be expressed by 

 symbols of classical chemistry. The question is whether our inabil- 

 ity to understand muscle is not due to the fact that what happens 

 further belongs to a different group of reactions which can no 

 more be described by these symbols, in which (E) is turned into 

 E*? This duality may hold for all reactions in which work, w is 

 produced, be it mechanical, osmotic, or electric work, etc. While 

 (£) may be the core of reactions in which substances are synthe- 

 tized and the living machinery is built, E* may be the core of re- 

 action in which this machinery is driven and work is produced. 

 This could explain why our notions, derived from intermediary 

 metabolism, did not lead us to a better understanding of muscular 

 contraction. 



When supposing a transformation of [E) into £* we are not 

 lost in the marshes of speculation, for the reaction on which all 

 •life is built is essentially such a transformation. This reaction is 



